1. Field of the Invention
The present invention generally relates to a conveyor, a method for conveying a semiconductor wafer and a method for manufacturing a semiconductor device. More particularly, the present invention relates to a conveyor for conveying a work using a conveyor belt mounted on a pulley.
2. Description of the Background Art
Conventionally, methods using a conveyor belt are used to convey a wafer as a work in the manufacturing process of a semiconductor or an integrated circuit such as IC (integrated circuit) or LSI (large scale integration).
FIG. 10 is a plan view of a conventional conveyor. FIG. 11 is a side view of the conveyor as viewed from the direction shown by arrow XI in FIG. 10. Referring to FIG. 10, the conventional conveyor 100 includes pulleys 41, 42, 43 and 44, and conveyor belts 11 and 12 mounted on the corresponding pulleys 41 to 44.
The conveyor belt 11 is mounted on the pulleys 41 and 43, and the conveyor belt 12 is mounted on the pulleys 42 and 44. A rotation shaft 45 connects the pulleys 41 and 42 to each other. A rotation shaft 46 connects the pulleys 43 and 44 to each other. The rotation shaft 45 is connected to a motor 48 through a driving shaft 47. Therefore, when the motor 48 rotates the driving shaft 47, the rotation is transmitted to the pulleys 41 and 42 through the rotation shaft 45. The pulleys 41 and 42 drive the conveyor belts 11 and 12. A semiconductor wafer 1 as a work is placed on the conveyor belts 11 and 12. Driving the conveyor belts 11 and 12 enables the semiconductor wafer 1 to be conveyed.
Referring to FIG. 11, the pulleys 42 and 44 have a disk shape, and are respectively provided with the rotation shafts 45 and 46 in the center thereof. When the rotation shaft 45 rotates in the direction shown by arrow R1, the pulley 42 also rotates in that direction. This allows the semiconductor wafer 1 on the conveyor belt 12 to be conveyed.
Note that the conveyor belts 11 and 12 are each formed from, e.g., an O ring of silicon rubber. The pulleys 41 to 44 are formed from, e.g., JIS (Japanese Industrial Standard) SUS303 stainless steel. A direct current (DC) motor is used as the motor 48.
Conventionally, in order to stop the semiconductor wafer 1 as a work at an arbitrary position, the semiconductor wafer 1 being conveyed is stopped with stoppers 51 and 52, and also rotation of the pulleys 41 and 42 is stopped. At this time, rotation of the conveyor belts 11 and 12 must be stopped as soon as the stoppers 51 and 52 are made in contact with the semiconductor wafer 1. This is because the conveyor belts 11 and 12 would otherwise slide on the semiconductor wafer 1. As a result, friction is generated between the semiconductor wafer 1 and the conveyor belts 11 and 12, scattering scrapings. This contaminates the semiconductor wafer 1, resulting in degraded quality of the semiconductor wafer.
Due to a large contact area between the semiconductor wafer 1 and the conveyor belts 11 and 12, sliding of the conveyor belts 11 and 12 on the semiconductor wafer 1 would produce belt-like flaws on the back surface of the semiconductor wafer 1. This also degrades the quality of the semiconductor wafer 1.
The present invention is made in view of the foregoing problems, and it is an object of the present invention to provide a conveyor capable of preventing degradation in quality of a work being conveyed.
A conveyor according to one aspect of the present invention includes: a conveyor belt; and a rolling element rotatably provided at a surface of the conveyor belt.
According to the conveyor structured as such, the rolling element is rotatably provided at the surface of the conveyor belt. By placing a work on the rolling element, the rolling element is interposed between the work and the conveyor belt. Therefore, the conveyor belt will not slide on the work even when it moves relative to the work. As a result, friction can be prevented from being generated between the work and the conveyor belt, preventing degradation in quality of the work.
Preferably, a plurality of rolling elements are provided along a conveying direction. In this case, the work can be supported with a plurality of rolling elements, enabling stable conveyance of the work.
Preferably, the conveyor further includes a holder provided at the surface of the conveyor belt, for rotatably holding the rolling element. In this case, the holder allows the rolling element to be stably held at the surface of the conveyor belt.
Preferably, the rolling element has a ball shape. In this case, the ball-shaped rolling element point-contacts the work, enabling the contact area between the work and the rolling element to be minimized. This can prevent damages (like a flaw) to the surface of the work being in contact with the rolling element, preventing degradation in quality of the work.
Preferably, the conveyor further includes a cleaning member for cleaning the rolling element. This enables the surface of the rolling element to be cleaned by the cleaning member, preventing a contaminant from adhering to the rolling element and the work.
Preferably, the conveyor belt conveys a semiconductor wafer.
A conveyor according to another aspect of the present invention includes: a conveyor belt; a pulley for driving the conveyor belt; a rotating means connected to the pulley so as to rotate the pulley; and a clutch mechanism for disconnecting the rotating means from the pulley when torque transmitted from the rotating means to the pulley exceeds a prescribed value.
In the conveyor structured as such, the clutch mechanism disconnects the rotating means from the pulley when the torque transmitted from the rotating means to the pulley exceeds a prescribed value. Accordingly, when the work being conveyed on the conveyor belt is stopped and thus the torque transmitted from the rotating means to the pulley exceeds a prescribed value, the rotating means is disconnected from the pulley. The pulley is thus stopped without being rotated by the rotating means, so that the conveyor belt will not slide on the work. As a result, degradation in quality of the work can be prevented.
Preferably, the rotation means includes a rotation shaft, and the clutch mechanism includes a ratchet mounted to the rotation shaft.
Preferably, the conveyor further includes a rolling element rotatably provided at a surface of the conveyor. In this case, the rolling element is rotatably provided at the surface of the conveyor. By placing a work on the rolling element, the rolling element is interposed between the work and the conveyor belt. Therefore, the conveyor belt will not slide on the work even when it moves relative to the work. As a result, friction can be prevented from being generated between the work and the conveyor belt, preventing degradation in quality of the work.
Preferably, a plurality of rolling elements are provided along a conveying direction. In this case, the work can be supported with a plurality of rolling elements, enabling stable conveyance of the work.
Preferably, the conveyor further includes a holder provided at the surface of the conveyor belt, for rotatably holding the rolling element. In this case, the holder allows the rolling element to be stably held at the surface of the conveyor belt.
Preferably, the rolling element has a ball shape. In this case, the ball-shaped rolling element point-contacts the work, enabling the contact area between the work and the rolling element to be minimized. This can prevent damages (like a flaw) to the surface of the work being in contact with the rolling element, preventing degradation in quality of the work.
Preferably, the conveyor further includes a cleaning member for cleaning the rolling element. This enables the surface of the rolling element to be cleaned by the cleaning member, preventing a contaminant from adhering to the rolling element and the work.
Preferably, the conveyor belt conveys a semiconductor wafer.
A method for conveying a semiconductor wafer according to the present invention includes the steps of preparing any one of the above conveyors; and conveying a semiconductor wafer using the conveyor.
A method for manufacturing a semiconductor device according to the present invention includes the steps of: preparing any one of the above conveyors; and conveying a semiconductor wafer using the conveyor.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.